1. Field of the Invention
The present invention relates to a plate lock-up mechanism used to mount a printing plate in an offset printing press, and a method for using that mechanism. In particular, the present invention relates to an apparatus and method for locking up a conventional, flat, printing plate into a cylindrical form prior to mounting of the plate on the plate cylinder of the offset printing press, to thereby ease the mounting or changing of the printing plate onto the plate cylinder.
2. Description of the Prior Art
Various prior art devices have been developed to make easier the mounting or changing of printing plates on the plate cylinder of a offset printing press. U.K. Published Patent Application No. 2 286 365 describes one prior art device for the quick exchange of printing plates on plate cylinders of a printing press. In the device shown in that publication, shown in FIGS. 1 and 2 of the present specification, the plate cylinder 1 includes an axial slot 2, and a side wall of the press includes an aperture (not shown). The printing plate 3 is bent into a cylindrical shape prior to being mounted on the plate cylinder 1. The ends 4, 5 of the plate 3 are bent and formed with a rounded edge 6 and a hook 7 to lock together and hold the plate 3 in the cylindrical shape. The cylindrically-bent and locked plate is then slid onto the plate cylinder 1 through the aperture in the press, such that the locked ends 4, 5 are inserted into the axial slot 2 in the plate cylinder 1. A lock-up mechanism 8 in the slot 2 is then engaged to lock the plate 3 to the plate cylinder 1.
A problem with the prior art device described above is that it requires complicated and sometimes difficult to make bends in the ends of the plate in order to hold the plate ends together during the mounting and lock-up operations.